Thursday, June 22, 2017

You're Not Forgetful, You're Just Efficient

For most people having a good memory
means being able to remember more information clearly for long periods of time.
For neuroscientists too, the inability to remember was long believed to
represent a failure of the brain's mechanisms for storing and retrieving
information.

But according to a new review paper
from Paul Frankland, a senior fellow in CIFAR's Child & Brain Development
program, and Blake Richards, an associate fellow in the Learning in Machines
& Brains program, our brains are actively working to forget. In fact, the
two University of Toronto researchers propose that the goal ofmemory
is not to transmit the most accurate informationover time, but to guide and optimize intelligent decision
makingby only holding on to valuable information.

"It's important that the brain
forgets irrelevant details and instead focuses on the stuff that's going to
help make decisions in the real world," says Richards.

The review paper, published this
week in the journal Neuron, looks at the literature on remembering,
known as persistence, and the newer body of research on forgetting, or
transience. The recent increase in research into the brain mechanisms that
promote forgetting is revealing that forgetting is just as important a
component of our memory system as remembering.

"We find plenty of evidence
from recent research that there are mechanisms that promote memory loss, and
that these are distinct from those involved in storing information," says
Frankland.

One of these mechanisms is the
weakening or elimination of synaptic connections between neurons
in which memories are encoded. Another mechanism, supported by evidence from
Frankland's own lab, is the generation of new neurons from stem cells. As new
neurons integrate into the hippocampus, the new connections remodel hippocampal
circuits and overwrite memories stored in those circuits, making them harder to
access. This may explain why children, whose hippocampi are producing more new
neurons, forget so much information.

It may seem counterintuitive that
the brain would expend so much energy creating new neurons at the detriment of
memory. Richards, whose research applies artificial intelligence (AI) theories
to understanding the brain, looked to principles of learning from AI for
answers. Using these principles, Frankland and Richards frame an argument that
the interaction between remembering and forgetting in the human brain allows us
to make more intelligent memory-based decisions.

It does so in two ways. First,
forgetting allows us to adapt to new situations by letting go of outdated and
potentially misleading information that can no longer help us maneuver changing
environments.

"If you're trying to navigate
the world and your brain is constantly bringing up multiple conflicting
memories, that makes it harder for you to make an informed decision,"
says Richards.

The second way forgetting
facilitates decision making is by allowing us to generalize past events to new
ones. In artificial intelligence this principle is called
regularization and it works by creating simple computer models that prioritize
core information but eliminate specific details, allowing for wider
application.

Memories in the brain work in a
similar way. When we only remember the gist of an encounter as opposed to every
detail, this controlled forgetting of insignificant details creates simple
memories which are more effective at predicting new experiences.

Ultimately, these mechanisms are
cued by the environment we are in. A constantly changing environment may
require that we remember less. For example, a cashier who meets many new people
every day will only remember the names of her customers for a short period of
time, whereas a designer that meets with her clients regularly will retain that
information longer.

"One of the things that
distinguishes an environment where you're going to want to remember stuff
versus an environment where you want to forget stuff is this question of how
consistent the environment is and how likely things are to come
back into your life, " says Richards.

Similarly, research shows that
episodic memories of things that happen to us are forgotten more quickly than
general knowledge that we access on a daily basis, supporting the old adage
that if you don't use it, you lose it. But in the context of making better
memory-based decisions, you may be better off for it.

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About Me

This is a blog about what interests me. Here you will find stories on animals, including animal rights material, cute stuff, and random informative posts about weird, beautiful and interesting creatures. Horses, Spotted Hyenas, and Border Collies will make regular appearances.
Also prominently featured will be posts about the Arts. Animation, photography, and the traditional forms, plus "outsider art," film and books.
Other things that will surface here are Japan & the Japanese, John Oliver, surfing, skateboarding and My Little Pony: Friendship Is Magic, interesting places and structures,and my own art, writing and photography.
There will be rants. It's an election year, and I am beginning to have a political dimension to my personality. I am also horrified at the level of injustice and violence visited upon people here in the US and elsewhere - particularly against people of color, immigrants, and the LGBT community. Some of these stories will be very hard to read, but I believe we must read them to keep ourselves mindful of the racist and vicious things that happen every day, to speak out when we see discrimination, and root out its evil from ourselves.